Several organs, muscles and nerves, e.g., kidneys, ureter, bladder, urethra, sphincters, and various other tissue, interact to collect, store and release urine. In vertebrates two kidneys filter waste and excess water from the bloodstream to form urine. The urine then flows from the kidneys to the bladder via a hollow muscular tube called a ureter. Normal urine flow occurs in only one direction, i.e., from the kidneys to the bladder. When urine backs up or flows in the other direction, i.e., from the bladder to the kidneys, infection or damage to the kidneys can occur.
The bladder is a hollow, balloon-shaped organ that sits in the pelvis. The bladder stores urine until the body is ready to release it. Normal adult human bladders can comfortably hold about 16 ounces or 2 cups of urine before needing to empty. Urine is produced and therefore the bladder fills based on the amount of excess water the body attempts to rid itself of. The bladder connects to another hollow tube, called the urethra, which allows the urine to pass outside the body. Circular muscles or sphincters surround and close tightly around the base of the bladder and urethra to prevent urine from leaking. Nerves in the bladder send a signal to the brain to let the body know when its time to urinate and the sphincters are relaxed to allow urine to pass.
The involuntary leakage of urine from the bladder is called urinary incontinence or stress incontinence. Stress incontinence is the loss of small amounts of urine associated with coughing, laughing, sneezing or other physical activities. This condition is essentially due to weak pelvic floor muscles. Stress incontinence is often caused by physical changes, such as pregnancy, childbirth, and menopause in women, and following a prostatectomy in men. While stress incontinence is the most common form of incontinence, it is treatable.
The field of urodynamics is devoted to studying and testing the functional disorders of the lower urinary tract which is comprised of the bladder and urethra. Urodynamics seeks to objectively confirm the existence of urological pathologies, such as urinary incontinence and blocked urine flow. In the field of urodynamics, the abdominal (Valsalva and coughing) Leak Point Pressure (LPP) of the human bladder is measured. Abdominal LPP is a very important measurement used to quantify the degree of incontinence in order to direct the right treatment. Measuring the abdominal LPP of the human bladder has traditionally required invasive, complicated, inconvenient and/or unclean procedures. These procedures typically include the insertion of a measuring device inside the pelvic area of the body, e.g., inserting a balloon catheter into the bladder or rectum. The undesirable nature of these procedures often acts as a deterrent to testing for many individuals in need of testing.